Exer12_27_TextQuery.h

// Warning: this header has inherent error. See notes in Exer12_27.cpp.
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
#include <memory>
class QueryResult;
std::ostream& print(std::ostream&, const QueryResult&);
class TextQuery{
friend class QueryResult;
friend std::ostream& print(std::ostream&, const QueryResult&);
public:
    using line_num = std::vector<std::string>::size_type;
    explicit TextQuery(std::ifstream &infile);
    QueryResult query(const std::string&);
private:
    std::vector<std::string> text;
    std::map<std::string, std::set<line_num>> word_line;
};
class QueryResult{
    friend std::ostream& print(std::ostream&, const QueryResult&);
public:
    QueryResult(const std::string& s, TextQuery::line_num cnt, TextQuery *text) : query_word(s), occurences(cnt), query_result(text) {}
private:
    const std::string query_word;
    TextQuery::line_num occurences = 0;
    // This is wrong.
    std::shared_ptr<TextQuery> query_result;
};
TextQuery::TextQuery(std::ifstream &infile)
{
    std::string line, word;
    line_num curr_line = 0;
    while(getline(infile, line))
    {
        std::istringstream word_breakup(line);
        text.push_back(line);
        while(word_breakup >> word)
        {
            (word_line[word]).insert(curr_line);
        }
        ++curr_line;
    }
}
QueryResult TextQuery::query(const std::string& str)
{
    line_num cnt = 0;
    auto find_rst = word_line.find(str);
    if(find_rst != word_line.end())
    {
        for(auto iter = find_rst->second.cbegin(); iter != find_rst->second.cend(); ++iter)
        {
            std::string output_line = text[*iter];
            std::istringstream is(output_line);
            std::vector<std::string> line_breakup;
            std::string out_word;
            while(is >> out_word)
                line_breakup.push_back(out_word);
            cnt += count(line_breakup.cbegin(), line_breakup.cend(), str);
        }
    }
    return QueryResult(str, cnt, this);
}
std::ostream& print(std::ostream& os, const QueryResult& q_rst)
{
    os << "element occurs " << q_rst.occurences << " times" << std::endl;
    if(q_rst.query_result.use_count() > 0)
    {
        std::shared_ptr<TextQuery> query_ptr = q_rst.query_result;
        auto iter = (query_ptr->word_line).find(q_rst.query_word);
        for(auto it = iter->second.cbegin(); it != iter->second.cend(); ++it)
            os << "(line " << *it << ") " << ((query_ptr->text)[*it]) << std::endl;
    }
    return os;
}